**Core Concept**
The dorsal artery of the penis is a branch of the internal iliac artery, supplying blood to the penis. It runs deep to the **deep fascia** of the penis, also known as the **tunica albuginea**. This anatomical relationship is crucial for understanding the vascular supply of the penis.

**Why the Correct Answer is Right**
The correct answer is related to the **deep fascia**, as the dorsal artery of the penis indeed passes beneath this layer. The **deep fascia** or **Buck's fascia** is a tough fibrous layer that surrounds the penis, playing a key role in its support and vascular supply. The dorsal artery's position beneath this fascia allows it to provide blood supply to the penile tissue.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the dorsal artery does not pass beneath the **dartos fascia**, which is a more superficial layer.
**Option B:** This option is incorrect because the **Colles' fascia** is also a superficial layer, not related to the dorsal artery's path.
**Option D:** This option is incorrect as it does not accurately describe the anatomical relationship of the dorsal artery.

**Clinical Pearl / High-Yield Fact**
Remembering the layers of the penis and their relationship to the vascular supply is crucial for understanding conditions like **priapism** and **penile fracture**. The **dorsal artery**'s position beneath the **deep fascia** is key to diagnosing and managing such conditions.

**Correct Answer:** C. deep fascia